Field
Embodiments of the disclosure relate generally to rotary actuators and more particularly to multiple shape memory alloy (SMA) tubes providing sequential or parallel rotation to an output shaft with ratchet supports for recovery.
Background
Rotary actuators are employed for numerous functions in various mechanical systems including aircraft. Many such actuators are powered by electrical motors which are larger than may be desirable for optimally locating the actuator, particularly in hinge line applications. Mechanical drive trains are therefore required which may add weight and complexity. Scaling of output torque of the rotary actuator typically requires multiple gear sets with a selectable transmission further increasing both the weight and complexity of the actuation system.
Shape memory alloy (SMA) actuators have been employed for hinge line actuation. However, such actuators tend to have limited torque generation. SMA tube actuator output scales with tube radius to the third power and scales with length. Radii of the tubes can be increased to meet torque requirement but larger tubes which can produce desired high torque values currently exceed fabrication capability.
It is therefore desirable to provide a rotary actuator which avoids requirements for extended mechanical drive trains and allows scaling of torque output without the added complexity of multiple gear sets or selectable transmissions.